?Inspired by the success of cemented paste backfill in the west orebody of Chambishi Copper Mine, integrated disposal of paste backfill and surface high-concentration tailings stacking was applied in the southeast orebody. This paper presents the integrated disposal system, including two deep cone thickeners, double-shaft horizontal mixer, two plunger pumps for underground backfill and three diaphragm pumps for surface stacking. The challenges of the integrated disposal system were deep backfilling (0.98 km) and long-distance discharging (15 km), so a combination of gravity flow and pumping was used in paste backfill and three diaphragm pumps with a preset pressure of 7 MPa were applied for surface stacking. The annual ore production in the southeast orebody is 3.3 Mt, which is 3.3 times larger than that of the west orebody. Therefore, the capacity of the integrated disposal system also needs to be expanded. The capacity of the paste backfill system and surface stacking system were 160 m3/h with paste concentration of 75 wt.% and 265 m3/h with slurry concentration of 55 wt.%, respectively. In the first phase, the cement to tailings ratios for primary and second stopes are 1/8 and 1/24 respectively. To meet the backfill strength and reduce the cost, waste rock will be added in paste backfill in the second phase, the waste rock to tailings ratio is 1/3, the cement to tailings and waste rock ratio for primary stopes are 1:12, and 1:30 for secondary stopes. As a result, the UCS after 28 days for primary and second stopes were 1.2 MPa and 0.5 MPa, respectively.
Cemented paste backfill (CPB) has been utilised globally in mines based on its benefits of non-segregation, non-bleeding and homogeneity. Due to a lack of research around the mechanism(s) driving anti-segregation properties, nowadays only some engineering empirical parameters including the slump or the fine particle content of backfill slurries can be used as the descriptive criterion for CPB. To better understand the antisegregation mechanism of CPB, so a quantitative criterion for its identification can be determined, the segregation-induced inhomogeneous properties of cemented tailings backfill have been experimentally investigated. Samples (diameter 75 mm and height 150 mm) with different solid contents were poured, cured and cut into sections of equal height. Thereafter, titration measures of EDTA-2Na and helium porosimeter have been used respectively to test the cement content and porosity of each section. Results show that the cement contents decreased from top to bottom along the curing height of samples, while the porosities increased along the settling direction. The inhomogeneity of cemented samples is affected obviously by the solids content of the paste, and it is notable that there is a turning point for the slurry concentration value over which the homogeneity will be improved dramatically. The turning point could be used as a new criterion for CPB definition from the perspective of inhomogeneity inhibition.
The objective during TSF beach development is to still maintain a slurry that is pumpable and self-distributing at the tailings storage facility (TSF), rather than having to rely on trucks or on conveyors and stacking systems to manage a cake, but one that will deposit at a steeper beach slope than can be achieved by thickening alone. The use of ultra paste has the potential to broaden the range of topographic conditions that will suit thickened tailings discharge. This paper presents a case study for a large copper mine in which underflow from a series of paste thickeners with a nominal tonnage of 3,660 tph at 59% solids concentration would be mixed with 1,363 tph of filter cake at 80% solids concentration. The combined tailings (ultra paste) would be discharged equally into two open channels (flumes) at the combined solids concentration of 63.5%. The ultimate goal of adopting an ultra paste scheme is to produce homogenous consistency tailings, hence proper mixing of the paste and filter cake has to occur. In this study based on a series of tests, the mixing requirement has been assessed. The study also covers a conceptual investigation of natural turbulent mixing (NTM) of the filtered tailings with paste thickened tailings and issues associated with the deposition of the combined tailings, the ultra paste, into the existing TSF. In the conclusion, the study indicates that NTM can possibly occur only for the case in which the total tailings are discharged into one channel, which is not practical due to limitations with regards to tailings management. Hence, mechanical mixing has been recommended in this case.
?Chile produces large amounts of tailings daily which must be safely disposed on the earths surface. There are a series of strategies that have been successfully used in our country to store tailings, among them are thickened and paste tailings. Paste tailings are an advantageous technique that allows for greater recovery of water while improving physical stability of the structure. Although challenges are faced worldwide when large production rates are tried to be thickened, the technique seems promising for countries like Chile where there is an ongoing water crisis. The stability of paste tailings facilities is highly influenced by water content or saturation. As consolidation occurs the tailings loses water. However, as the evaporation front takes place, the material goes from a saturated to a non-saturated state. Unsaturated paste has shown improved resistance, e.g. liquefaction resistance almost double when saturation drops below 90%. A well planned facility operation should consider the monitoring of the water content of the paste. However, this is sometimes difficult, due to the large areas that must be controlled and the danger associated with manual moisture measurements in the field. In this context, we proposed the use of hyperspectral cameras to obtain a relationship between the paste moisture content and light reflectance. This would allow to generate moisture surface map and to the use of this data to monitor for instance evaporation rates or water balance in tailings storage facilities. This article summarizes laboratory main findings and proposes a series of procedures to implement the technique in the field.
Paste thickening represents a proven and effective method for the safe disposal of tailings and maximises water recovery. The optimum density for disposal is often at the limits of that achievable in commercially available thickeners. This paper looks at the options available to increase paste density to meet the disposal requirements and to stabilise paste properties through blending filtered tailings with thickened tailings, supported by experimental data and case studies.
?Tailings transport is an integrated element in any wet tailings storage facility (TSF). Tailings from the process plant are often thickened to a moderate or relatively high (but still pumpable) solids concentration, depending on several parameters mainly the TSF deposition requirements and strategies, process plant water security status and the dewatering technology utilised. This paper overviews the transportation of paste and thickened tailings and discusses various aspects and considerations in the hydraulic design of the system. Material characteristics, flow behaviour assessment (rheological behaviour measurement and interpretation) and the basis of design definition are discussed. The recent developments in environmental authorities regulations associated with the tailings pipeline burst and leakage management are also reviewed in this paper. The tailings leakage and spillage to the environment is one the main concerns for any tailings hydraulic transportation system, therefore as part of the tailings pipeline design, the pipeline integrity failure (due to pipe wear, overpressure bursting etc.) should be thoroughly analysed to propose proper mitigation measures. The paper discusses a methodology to assess the potential tailings volume release to the environment in an event of the pipeline integrity failure which would be of interest to the operators and designers.
Cemented paste backfill (CPB) has become known as a superior secondary ground support technique and mine tailings storage method for stoping. Extensive scientific research has been conducted by the authors on CPB to provide the Red Lake operation (RLO) of Evolution Mining with an optimised backfill placement process. Due to these complex factors and interactions, a rational CPB material design process was assessed to demonstrate the safety aspects related to a continuous pour. For this purpose, an extensive field monitoring program was required to quantify the CPB performance and characteristics. There are two different ways of optimising the CPB design to maximise placement rate: (i) optimising the type and amount of binder added to the system, and (ii) optimising the CPB placement process underground. Optimisation of binder type and dosage is relatively easy as the required backfill stand-up strength is based on block dimensions, stope stability, and extraction sequencing. Four stopes were instrumented with total earth pressure cells (TEPCs) and piezometers to capture the pressures acting on the fill fence structures and the strengthening response of the CPB plug within the stopes. This paper summarises the results of each of the tests performed. Based on the results obtained from this study, it was concluded that RLO can safely conduct continuous CPB pours with appropriate safeguards and protocols in place. It is important to note that this paper is a summary of the CPB performance and characteristics in RLO longhole stopes and does not reflect site-specific safety procedures, protocols, and critical controls required for a more aggressive pouring regime.
This paper looks at the design of a paste reticulation system, particularly a new method of diverting paste flows in critical situations, and the safeguards that were incorporated into the reticulation design to minimise the risk of line blockage during backfill operations. It also details the actions taken during a paste blockage event to flush and recover the entire line. The paper considers some of the restrictions that were imposed due to cost and time restraints on the schedule, and the impact these restrictions had on the profile and the flow characteristics of the reticulation network. Finally, a summary of key learnings and solutions that have been implemented to further safeguard the system has been provided.
The paper will present a new pulsation reduction system (PRS) invented by MHWirth. This PRS is in contrast to conventional pulsation damperssuitable to eliminate high-frequency pulsation of reciprocating diaphragm pumps. Brief description of functionality: The new damper is connected to the propelling fluid chamber of the diaphragms. The propelling fluid, a hydraulic oil, is used as a damping medium, converting the pulsation energy described above into heat by throttle effects. This effect is similar to a shock absorber. The paper will also explain the PRS effects, present operational data from field application and address the following benefits by using it in a tailings and storage facility:
As backfill systems become a more common method for managing tailings and enhancing ore recovery, safe and efficient methods for handling the backfill are adding value for mine owners. At Kirkland Lake Gold Fosterville mine (Victoria, Australia), automated diverter valves were installed at distribution switching points to direct paste to the intended stopes. The valves are operated remotely from a control room, removing the human element at the transition point during diversion. The other option for making changes in paste distribution is a manual operation where long sweep elbows are disconnected from the piping network and reconnected to a different downstream pipe. This process is tedious and time consuming, requiring many man hours and equipment that is not always readily available, resulting in much down time. This paper will discuss how using automated diverter valve operation in place of manual diversion of the paste at Kirkland Lake Golds reticulation system delivered dramatic uptime and minimised physical safety risks. Safety benefits not only eliminated the manual movement of piping components but include localised lockout access, safe evacuation of paste from upstream borehole (and piping) resulting from downstream blockage and diversion of flush water to a suitable collection area.